Buckle

ABSTRACT

A buckle is provided in which a number of parts can be reduced and which can reliably maintain a latched state. When a tongue plate is engaged (latched) by a lock plate, presser members of a cam urged by a return spring abut receiving surfaces of the lock plate, and therefore, a latched state cannot be inadvertently released. Further, when the latched state is to be released, by pressing a release button, a claw is pushed such that a cam rotates, and the presser members separate from the receiving surfaces. As a result, the return spring is compressed, and due to elastic force of the return spring, the release button returns to its original position. In this way, because the return spring carries out both the operation of urging the cam and the operation of returning the release button to its original position, the number of parts is reduced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a buckle which engages with a tongueplate provided at a webbing of a seat belt device so as to maintain thewebbing in an applied state.

2. Description of the Related Art

Conventional seat belt devices use a buckle which engages with a tongueplate so as to maintain a webbing in an applied state. The buckleincludes, within a cover member, a buckle main body, a lock plate whichengages with the tongue plate so as to be in a latched state, a releasebutton which releases the latched state of the lock plate, an ejectorwhich expels the tongue plate to the exterior by elastic force at thetime the latch state is released, a lock pin for maintaining the latchedstate, and the like.

Simplification of the processes for manufacturing the buckle which isstructured in this way is desired, and a reduction in the number ofparts is desired from the standpoint of a reduction in costs.

Further, a mechanism which keeps the latched state of the lock plate tothe tongue plate from being released even when an unplanned force isapplied to the buckle is indispensable.

SUMMARY OF THE INVENTION

In view of the aforementioned, an object of the present invention is toprovide a buckle in which the number of parts is reduced and which canreliably maintain a latched state.

A first aspect of the present invention is a buckle which engages with atongue plate provided at a webbing in a seat belt device, comprising: alatch member engaging with the tongue plate which has been inserted to apredetermined position; a lock member abutting the latch member andmaintaining an engaged state in which the latch member is engaged withthe tongue plate; an operation member which, when operated, releases thelock member from the latch member; and a spring disposed between theoperation member and the lock member, and urging the operation member toa pre-operation original position, and urging the lock member toward thelatch member.

Operation of the first aspect will be described.

Due to the tongue plate being inserted in the buckle up to apredetermined position, the latch member engages the tongue plate so asto be in a latched state. At this time, the lock member, which is urgedby the elastic force of the spring, abuts the latch member, and locksthe latch member such that the latch member cannot be displaced from theengaged state. As a result, the latched state is maintained.

When the tongue plate is to be released from the buckle, by operatingthe operation member against the elastic force of the spring, the lockmember separates from the latch member, and the locked state of thelatch member is released. As a result, the engaged state of the latchmember and the tongue plate is released, and the tongue plate is freedto the exterior, and the operation member is returned to its originalposition by the elastic force of the spring.

In this way, a single spring serves as both a spring for making the lockmember abut the latch member and a spring for returning the operationmember to its original position. Accordingly, the number of parts can bereduced, and the manufacturing process and assembly process can besimplified.

Further, because the latch member is locked by the lock member which isurged by the spring, the latched state is reliably maintained.

In a second aspect of the present invention, in the first aspect, thelock member is a freely rotating cam, and comprises: a first convexportion pushed in a lock releasing direction by operation of theoperation member; and a second convex portion formed at a side of acenter of rotation of the cam which is substantially opposite the sideat which the first convex portion is disposed, an end of the springengaging with the second convex portion, wherein a center of gravity ofthe cam is positioned toward the second convex portion.

Operation of the second aspect will be described.

When the latch member engages the tongue plate which has been insertedin the buckle up to a predetermined position (i.e., when the latchedstate is set), the lock member (cam) urged by the spring rotates, andthe lock member (the second convex portion) abuts the latch member. As aresult, the latch member is locked, and the latched state is maintained.

When the latched state is to be released, by operating the operationmember, the first convex portion is pressed, and the lock member rotatesin the lock releasing direction. As a result, the lock member separatesfrom the latch member, and the locked state is released. As a result,the engaged (latched) state of the latch member and the tongue plate isreleased.

At this time, the operation member is returned to its original positiondue to the urging force of the spring.

The implementing and releasing of the latched state are carried out inthis way. However, when an impact force in the lock releasing directionacts on the buckle, because the first convex portion and the secondconvex portion are disposed at substantially opposite sides of thecenter of rotation of the cam, rotational moments in opposite directions(the lock releasing direction and the direction opposite thereto) act onthe first convex portion and the second convex portion. However, becausethe center of gravity of the lock member (cam) is positioned toward thesecond convex portion side, a rotational moment in the directionopposite to the lock releasing direction acts on the lock member.Accordingly, the latched state (locked state) of the buckle is notreleased due to the impact force, and is reliably maintained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a buckle relating to anembodiment of the present invention.

FIG. 2 is a cross-sectional view of main portions at a time the bucklerelating to the embodiment of the present invention is free.

FIG. 3 is a cross-sectional view of main portions at a time the bucklerelating to the embodiment of the present invention is latched.

FIG. 4 is a plan view of main portions at the time the buckle relatingto the embodiment of the present invention is latched.

FIG. 5 is a schematic view for explaining application of force at a timea lock plate relating to the embodiment of the present inventionreleases a latched state.

FIG. 6 is a schematic view for explaining a state in which force isapplied to a cam relating to the embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

A buckle relating to an embodiment of the present invention will bedescribed hereinafter with reference to FIGS. 1-6.

As illustrated in FIG. 1, the buckle 10 is formed from a cover member12, a body 14, an ejector 18 which urges a tongue plate 80, which willbe described later, toward the exterior by the elastic force of anejector spring 16, a lock plate 20 which is in a latched state byengaging with the tongue plate 80, a cam 22 which abuts and moves awayfrom the lock plate 20 so as to maintain or release the latched state,and a release button 26 which engages with the cam 22 due to a returnspring 24 and is pressed at the time of releasing the latched state.

A through hole 30 is formed in the cover member 12. All of theaforementioned structural elements are disposed at the interior of thethrough hole 30.

The body 14 is formed by a bottom surface 14A and a pair of sidesurfaces 14B which are formed integrally with the bottom surface 14A atthe both sides thereof, such that the body 14 is formed in a substantialU-shape. As illustrated in FIG. 2, the bottom surface 14A of the body 14is connected, via a rivet joint 34, to an anchor plate 32 which isinserted from one end (the arrow X1 direction end portion; hereinafter,the arrow X1 direction will be referred to as the X1 direction) of thethrough hole 30 (see FIG. 2). A hole 36 for sliding for the ejector 18is formed in the bottom surface 14A.

The ejector 18 has a configuration in which a top plate 18A and a bottomplate 18B are connected together by a connecting portion 18C which isthinner than both. Accordingly, due to the connecting portion 18C of theejector 18 being inserted into the hole 36 for sliding of the body 14,the top plate 18A abuts the upper side of the bottom surface 14A, andthe bottom plate 18B abuts the bottom side of the top surface 14A.Namely, the ejector 18 is structured so as to slide freely along thelongitudinal direction (the X direction) of the hole 36 for sliding. Theejector spring 16 is disposed between a projection 40 formed at the rearsurface (the X1 direction side) of the ejector 18 and a projection 38formed at the X1 direction end portion of the hole 36 for sliding. Theejector spring 16 always urges the ejector 18 in the arrow X2 direction(hereinafter referred to as the X2 direction).

A pair of supporting portions 42 for supporting the lock plate 20 areformed at the rear (X1 direction) of the upper portion of the bothtransverse (Y) direction end portions of the ejector 18.

At the central portion in the transverse direction (Y direction) at thefront end portion (X2 direction end portion) of the lock plate 20, anengaging portion 50, which is bent downward substantially 90° as viewedfrom the side, is formed, and a pair of receiving surfaces 52, at whichare formed downwardly convex circular arc-shaped surfaces as seen fromthe side, are formed at the both transverse direction sides of theengaging portion 50. Further, pairs of supporting plates 54, 56 andengaging plates 58 formed so as to be slanted downward are formed atboth transverse (Y) direction end portions of the rear end portion (X1direction end portion) of the lock plate 20.

The supporting plates 54, 56 of the lock plate 20 are inserted intopairs of concave portions 60, 62 provided at both side surfaces 14B ofthe body 14. The lock plate 20 is swingable in the directions of arrow A(see FIGS. 2 and 3) with this region as the center of swinging.

The cam 22 is disposed at the top portion of the lock plate 20. A shaft66 inserted through a hole 64 is supported at holes 68 formed in theboth side surfaces 14B of the body 14, such that the cam 22 is supportedso as rotate freely in the directions of arrow B (see FIGS. 2 and 3).

A claw 70 is formed at the top side of the cam 22. In the latched state,the claw 70 abuts the release button 26 which will be described later.

At the bottom side of the cam 22 (the opposite side approximately 180°from the claw 70 in the B direction), a hook 74, with which one end ofthe return spring 24 is engaged, is formed at the transverse (Y)direction center, and a pair of presser members 72, having pressersurfaces 72A of configurations (circular-arc-shaped surfaces as seenfrom the side) corresponding to the receiving surfaces 52 of the lockplate 20, are formed at the transverse (Y) direction both sides. One endof the return spring 24 is engaged with the hook 74, and the other endof the return spring 24 is engaged with a convex portion 76 (see FIGS. 2and 3) of the release button 26.

As illustrated in FIG. 4, the release button 26 is provided with a pairof protrusions 26A which slide on the top surfaces of the both sidesurfaces 14B of the body 14. The end portions of the protrusions 26Aabut the claw 70 of the cam 22 at the time of latching.

An engaging hole 82 for engaging the lock plate 20 is formed in thefront end portion (X1 direction end portion) of the tongue plate 80which is inserted into the buckle 10.

Operation of the buckle 10 which is structured in this manner will bedescribed.

The state of the buckle 10 before the tongue plate 80 has enteredtherein is illustrated in FIG. 2.

At this time, because the ejector 18 is always urged in the X2 directionby the ejector spring 16, the ejector 18 is positioned at the X2 sideend portion of the hole 36 for sliding. Accordingly, as illustrated inFIG. 2, at the lock plate 20, the engaging portion 50 is supported bythe inclined surfaces forming the supporting portions 42 of the ejector18, and the lock plate 20 is in a state of having been rotated in thearrow A1 direction (hereinafter referred to as the Al direction) withportions of the supporting plates 56 as the center of rotation. The lockplate 20 abuts the shaft 66 of the cam 22.

In this state, the tongue plate 80 is inserted from the X2 directionside of the through hole 30 of the cover member 12. Namely, the tongueplate 80 presses the ejector 18 in the X1 direction, and the enters inthe direction of X1 while compressing the ejector spring 16. At thistime, the supporting portions 42 of the ejector 18 separate from theengaging portion 50 of the lock plate 20 as the ejector 18 moves in theX1 direction.

Due to the distal ends of the supporting portions 42 abutting theengagement plates 58 of the lock plate 20 due to movement of the ejector18 (refer to the two-dot chain line portion in FIG. 2), the engagementplates 58 are pressed in the X1 direction. Namely, a counterclockwise(arrow A2 direction, hereinafter referred to as A2 direction) momentaround the supporting plates 56 is generated at the lock plate 20, andthe engaging portion 50 is inserted into the engaging hole 82 of thetongue plate 80 (see FIG. 3).

Because the lock plate 20 separates from the cam 22 due to the lockplate 20 rotating in the A2 direction, the cam 22 which is always urgedin the X1 direction by the return spring 24 rotates counterclockwise(the arrow B1 direction, hereinafter referred to as the B1 direction).The rotation of the cam 22 stops due to the claw 70 abutting theprotrusions 26A of the release button 26. As a result, as illustrated inFIG. 3, the presser members 72 (presser surfaces 72A) of the cam 22 abutthe receiving surfaces 52 of the lock plate 20, and clockwise (A1direction) rotation of the lock plate 20, i.e., releasing of the latchedstate, is prevented.

Next, the case in which the tongue plate 80 is pulled out will bedescribed with reference to FIGS. 3 and 4.

In this case, first, the release button 26 is pressed-in in the X1direction. In this way, the protrusions 26A of the release button 26press the claw 70 of the cam 22, and the cam 22 is rotated clockwise (inthe arrow B2 direction, hereinafter referred to as the B2 direction)while compressing the return spring 24. Namely, the presser members 72(presser surfaces 72A) of the cam 22 which were locking the lock plate20 separate from the receiving surfaces 52 of the lock plate 20.

As illustrated in FIG. 5, at the lock plate 20, X1 direction force Fapplied by the ejector spring 16 is applied to the engaging portion 50from an X1 direction end surface 80A forming the engaging hole 82 of thetongue plate 80. This force F is dispersed into a force F1, which is aradial direction component which is disposed on a line connecting acenter of rotation C (supporting members 56) of the lock plate 20 andthe point of application of force, and a force F2 which is a componentin a direction orthogonal to the force F1. Due to the force F2, arotational moment in the A1 direction around the supporting plates 56 isapplied to the lock plate 20.

Accordingly, due to the presser surfaces 72A of the cam 22 separatingfrom the receiving surfaces 52 of the lock plate 20, the lock plate 20is rotated in the A1 direction. As a result, the engaging portion 50comes out from the engaging hole 82 of the tongue plate 80. In this way,the tongue plate 80, which was urged in the X2 direction by the ejector18, is released from the buckle 10 in the X2 direction.

On the other hand, when the amount of compression of the return spring24 exceeds a predetermined amount, the release button 26 returns to itsoriginal position (moves in the X2 direction) due to the elastic forceof the return spring 24.

At the buckle 10 of the present embodiment, the cam 22, which maintainsthe latched state of the lock plate 20, is maintained at a predeterminedposition due to the elastic force of the return spring 24, and thereturn of the release button 26 to its original position also occurs dueto the elastic force of the return spring 24. Namely, due to the returnspring 24 being used for these two operations, the number of parts canbe reduced.

As illustrated in FIG. 6, in a case in which an impact force G isapplied in the X1 direction when the buckle 10 is in a latched state,the X1 direction force is applied to the release button 26 and the claw70, a rotational moment M1 in the B2 direction acts on the cam 22, andsimultaneously, a rotational moment M2 in the B1 direction acts on thepresser members 72 and the hook 74. Accordingly, if the weight of thepresser members 72 and the hook 74 of the cam 22 is made sufficientlylarge, the rotational moment M2 is greater than the rotational momentM1. Namely, if the center of gravity of the cam 22 is positioned at theside of the presser members 72 and the hook 74 with respect to thecenter of rotation, even if the impact force G is applied to the cam 22,only the B1 direction rotational moment is applied. Accordingly,movement of the cam 22 in the B2 direction and releasing of the latchedstate due to the impact force G can be reliably prevented.

This can be achieved by, for example, forming a configuration in whichthe center of gravity at the cam 22 is positioned at the presser members72 and hook 74 side, or by forming the cam 22 from a sintered alloy orthe like whose relative mass is large.

Further, by sufficiently guaranteeing the weight of the cam 22 (thepresser members 72 and the hook 74), even if the weight of the releasebutton 26 formed from plastic or the like is added, the releasing of thelatched state due to the impact force G can be reliably prevented.

In the first aspect of the invention, the number of parts of the bucklecan be reduced while maintaining a structure in which the latched statecan be maintained.

In the second aspect of the invention, the latched state can be evenmore reliably maintained while the number of parts is reduced.

What is claimed is:
 1. A buckle which engages with a tongue plateprovided at a webbing in a seat belt device, comprising: a latch memberengaging with the tongue plate which has been inserted to apredetermined position, and having follower surfaces; a lock member,which is a freely rotating cam, slidably engaging said follower surfacesof said latch member and maintaining an engaged state in which saidlatch member is engaged with the tongue plate; an operation memberwhich, when operated, releases said lock member from said latch member;and a spring disposed between said operation member and said lockmember, and urging said operation member to a pre-operation originalposition, and urging said lock member toward said latch member.
 2. Abuckle according to claim 1, wherein said lock member comprises: a firstconvex portion pushed in a lock releasing direction by operation of saidoperation member; and a second convex portion formed at a side of acenter of rotation of said cam which is substantially opposite the sideat which said first convex portion is disposed, an end of said springengaging with said second convex portion, wherein a center of gravity ofsaid cam is positioned toward said second convex portion.